Yep, long as there wasn't heroic effort involved in making the piston move, soaking and getting things moving slowly probably won't be a problem. (I guess I mixed in fishhead's comment about beating the shizzle loose in a different motor.
) Loosening and 'washing' seems to work on a lot of these small motors, since much of the stuff that needs rinsing is corrosion effects rather than carbon, the usual cause of sticking rings.